The present invention relates to a process for the production of readily polymerizable vinylaromatic compounds. More particularly, the present invention relates to a process for the removal of polymers which collect in the apparatus utilized in the production of vinylaromatic compounds.
It is well known that monomeric styrene, vinyltoluene, alkylated styrene, divinylbenzene, and other vinylaromatic compounds polymerize very readily, and furthermore, that the rate of polymerization increases at elevated temperatures. Since vinylaromatic compounds, produced by common industrial methods, contain impurities, these compounds must be subjected to separation and purification processes in order to be suitable for most types of further industrial use. Such separation and purification is generally accomplished by distillation.
In order to prevent polymerization of vinylaromatics during distillation, various types of known polymerization-inhibitors have been employed in connection with prior art distillation processes. Only a very few of these compounds have proved to be of any utility for inhibiting polymerization under distillation conditions, and even fewer are effective in the columns of the distillation apparatus.
The cross-linked polymer which may collect in the production apparatus is a hard material insoluble in ordinary solvents such as benzene or carbontetrachloride. The problem is particularly acute in, for example, the recycle columns of the distillation apparatus. The progressive growth of such deposits not only reduces the effective yield of commercial vinylaromatic monomer production processes, but also fouls lines, pumps, fractionators and other distillation equipment, thereby reducing the run length of the production apparatus and increasing the production cost of the desired vinylaromatic monomer. As these polymer deposits are insoluble, cleaning of the production equipment has required manually chipping the hard polymer out of the clogged apparatus.
Though efforts directed toward the reduction and elimination of polymer buildup shown promise, it is not yet possible to completely avoid polymer buildup over periods of prolonged operation. Thus, there exists a strong need for an improved process for removing the insoluble polymer from vinylaromatic compound production apparatus.